If Kelan takes fatal damage, he enter in statis for 1 second, and then revives with all his life and mana. 5 seconds thereafter or when his health reach zero again, he really die. However, if he gets a kill during the 8 seconds, he stays alive, and if he gets an assist his respawn time will be halved.
Last Will's cooldown is static and is unaffected by cooldown reduction.

Soul Drain

RANGE: 600

COST: 80 / 85 / 90 / 95 / 100 mana

COOLDOWN: 12

Active: Kelan instantly deals magic damage to the target and then leash himself to it for up to 5 seconds. As long as the leash keeps up, Kelan will continue to deal damage while increasing his attack speed and reducing the target's attack speed by half the same percentage. The drain last 8 seconds after the leash broke, and decays over the last 5 seconds. The attack speed debuff does not affects bonus attack speed, like those from items.

Leash Range: 800

Initial Damage: 40 / 70 / 100 / 130 / 160 (+50% AP)(+65% bonus AD)

Max Damage: 80 / 140 / 200 / 260 / 320 (+100% AP)(+130% bonus AD)

Attack Speed gained per second: 8% / 10% / 12% / 14% / 16%

Max Attack Speed gain: 40% / 50% / 60% / 70% / 80%

Attack Speed lost per second: 4% / 5% / 6% / 7% / 8%

Max Attack Speed lose: 20% / 25% / 30% / 35% / 40%

Ravaging Torment

COST: 50 mana

COOLDOWN: 15

Passive: Kelan's attacks apply a slow to their target for 1.75 seconds that stacks up to 3 times.

Slow per stack: 8% / 9% / 10% / 11% / 12%

Max Slow: 24% / 27% / 30% / 33% / 36%

Active: For the next 5 seconds, Kelan's attacks deals bonus magic damage and apply a 2.5 seconds crowd control vulnerability, causing all crowd control on that target to last longer.

Damage: 20 / 35 / 50 / 65 / 80 (+15% AP)(+25% bonus AD)

Crowd control Vulnerability: 10% / 13.75% / 17.5% / 21.25% / 25%

Spectral Shroud

COST: 70 / 80 / 90 / 100 / 110 mana

COOLDOWN: 22 / 20 / 18 / 16 / 14

Active: Create a 275 radius Spectral Shroud at Kelan's position for 5 seconds. While on the shroud, Kelan ignores unit collision, moves faster and gains armor and magic resistance. If an enemy champion enter the main shroud, he will leave 150 radius shrouds that last for 2 seconds where he walks for 4 seconds. Continual exposures renews the debuff.

Movement Speed: 5% / 8% / 11% / 14% / 17%

Armor and magic resistance: 10 / 20 / 30 / 40 / 50

Haunt

RANGE: 700

COST: 125 / 150 / 175 mana

COOLDOWN: 240 / 210 / 180

Active: Kelan dashes to the target enemy champion and then fuses with him for several seconds during which Kelan is untargetable. For the duration, the target become an ally that Kelan control and takes 50% reduced damage from towers, but cannot be healed or buffed by Kelan's allies or uses the target's item's active, abilities and summoner spells but can uses his own from the host's body. When reactivating the ability or the duration ends, Kelan leaves his host, dealing magic damage and leaving it silenced and slowed for 1.5 seconds. Any ability you use for the duration will uses Kelan's stats.